Have you tried updating the firmware?
I was having the same problem but intermittently, after a firmware update it's stopped 99% of the time, the other 1% I put up the the gd-01 headunit being dodgy from the start.
There hasn't been an update for the GD-01 system in over 5 years, unless the vehicle had never been serviced at a Hyundai dealership there wont be anything new.
The 01 units are well known for issues from audio not working to completely dead units which I had in my own vehicle.
There is a Australian repair shop that quotes $700 to fix the GD-01 units, though far cheaper than Hyundai's $1400 replacement cost
it's a far better option upgrading to the GD-03.